Surgical staplers have been used in the prior art to simultaneously make a longitudinal incision in tissue and apply lines of staples on opposing sides of the incision. Such instruments commonly include a pair of cooperating jaw members that, if the instrument is intended for endoscopic or laparoscopic applications, are capable of passing through a cannula passageway. One of the jaw members receives a staple cartridge having at least two laterally spaced rows of staples. The other jaw member defines an anvil having staple-forming pockets aligned with the rows of staples in the cartridge. The instrument includes a plurality of reciprocating wedges which, when driven distally, pass through openings in the staple cartridge and engage drivers supporting the staples to effect the firing of the staples toward the anvil.
The simultaneous severing of tissue while forming rows of staples on each side of the cut reduces bleeding and simplifies the surgical procedure. However, an appropriate amount of tissue should be clamped between the jaws so that proper staple formation is achieved and so that a cutting member does not bind or otherwise fail to fully cut the clamped tissue.
A stapling and severing instrument that maintains a maximum jaw spacing is described in U.S. Pat. No. 4,429,695. In particular, a central knife carrier has an upper shoe that enters an upper passageway through an opening when the upper jaw is closed and has a lower shoe that is received within a lower passageway of the lower jaw. Thus, as the knife carrier is advanced distally, the shoes vertically and laterally position the upper and lower jaws. U.S. Pat. No. 4,429,695 teaches that the shoes are attached to the central knife carrier to resist vertical deflection (opening) of the jaws during ejection and forming of staples. As taught, the forces tend to vertically open the jaws during stapling. However, no mention is made of resisting forces that might be applied to vertically close the jaws. Additionally, this reference teaches that the device described therein is assembled from two separate, unconnected elements that are brought together and clamped onto tissue. The two elements form a device suitable only for an open procedure that has no size limitations.
Increasingly, endoscopic and laparoscopic procedures are preferred over open procedures due to their reduced post-operative recovery times and other advantages. Endoscopic stapling and severing instruments use a long slender jaw member that tends to deflect upwardly when clamped onto thick tissues. On thick tissue, this upward deflection of the free (distal) end of the jaw can cause differences in height of the formed staples as the distal gap between the anvil and cartridge is larger than the proximal gap. To ensure more uniform proximal to distal staple formation, the anvil is frequently cambered or bent inwardly toward the staple cartridge. This camber is better for thick tissue and can cause tighter staple forms at the distal end when used on thin tissue. To overcome this tight distal closure, pins or bumps have been added to the clamping surface of the cartridge adjacent to the distal end of the cartridge. The closure of the anvil onto the pin ensures a minimum gap at the distal end. However, surgeons were concerned about the pins or bumps causing tissue trauma. What is needed is a mechanism for maintaining a minimal gap between the anvil and cartridge and a mechanism for maintaining a maximum gap between the anvil and cartridge.
An example of a surgical stapler suitable for endoscopic applications is described in U.S. Pat. No. 5,465,895, which advantageously provides distinct closing and firing actions. Thereby, a clinician is able to close the jaw members upon tissue to position the tissue prior to firing. Once the clinician has determined that the jaw members are properly gripping tissue, the clinician can then fire the surgical stapler, thereby severing and stapling the tissue. The simultaneous severing and stapling avoids complications that may arise when performing such actions sequentially with different surgical tools that respectively only sever or staple.
One specific advantage of being able to close upon tissue before firing is that the clinician is able to verify via an endoscope that a sufficient amount of tissue has been captured between opposing jaws. Otherwise, opposing jaws may be drawn too close together, especially pinching at their distal ends, and thus not effectively forming closed staples in the severed tissue. Moreover, a firing bar that traverses between opposing jaws to sever the tissue and to drive the wedges that drive the staples may encounter resistance due to the pinched opposing jaws.
Thus, while such surgical staplers have been a significant advance in surgical procedures, an opportunity has been recognized for enhancing their effectiveness. In particular, it would be desirable to affirmatively maintain proper spacing between the opposing jaws during firing, both opening and closing deflections. In particular, endoscopic devices need to fit into an access device such a trocar, and must maintain a small shaft diameter. To date, no endoscopic stapling device has been provided that has room for a pair for longitudinal passageways for shoes on a cutter that resists both tensile and compressive jaw loadings.
Furthermore, it is desirable to maintain other advantages of U.S. Pat. No. 5,465,895 to include a wedge sled integral to a staple cartridge, rather than having camming surfaces attached to a cutter. Thereby, fabrication of the cutter is simplified, as is installation of the staple cartridge. Significantly, an integral wedge sled may be designed specifically for each size and application of a staple cartridge, allowing the stapling and severing instrument increased number of uses. In particular, the thickness of the staple cartridge may be based on the desired tissue thickness. Also, the number and spacing of rows of staples may vary.
Consequently, a significant need exists for an improved surgical stapling and severing instrument that maintains proper spacing in its end effector to achieve proper stapling of the severed tissue, yet retains the advantages of a staple cartridge having an integral wedge sled.